In a known electrostatic holding apparatus for attracting and holding an object to be adsorbed by use of the Coulomb force of static electricity, an insulating base layer, a set of electrodes, and an adsorbing layer are sequentially laminated. In such apparatus, positive and negative charges are respectively applied to the set of electrodes by conduction, and the adsorbing layer is induced, whereby an object to be adsorbed is adsorbed and held by the electrostatic attracting force of the adsorbing layer. Such electrostatic holding apparatus is disclosed in JP-B No. 55-20830 and JP-B 57-58872.
However, such conventional electrostatic holding apparatuses have a disadvantage in that, when the adsorbed object is peeled off or removed from the apparatus, the attracting force is weakened. Thus, when a further object is to be attached to the apparatus, there is a problem in that a sufficient attracting force may not be effected, and the object to be adsorbed may not be stably held.
It is, therefore, an object of the present invention to provide an improved electrostatic holding apparatus of this general type, which apparatus overcomes the above disadvantage.
To accomplish this object, according to the invention, there is provided an electrostatic holding apparatus having, sequentially laminated, an insulating base layer, a set of electrodes to which positive and negative charges are respectively applied by conduction, and an adsorbing layer which is induced by the set of electrodes and adsorbs and holds an object to be adsorbed by an electrostatic attracting force. This apparatus is characterized by providing a power supply circuit for respectively applying the opposite (i.e., reversing the) positive and negative charges to the set of electrodes after the object adsorbed and held to the adsorbing layer is peeled off so that a new object can be adsorbed and held by the apparatus.
According to the invention, after completion of the non-conduction state (that is, after removal of the object), the opposite positive and negative charges are respectively applied to the set of electrodes by the power supply circuit. Therefore, by setting the apparatus into the non-conducting state, the object held on the apparatus can be easily peeled off. On the other hand, by applying the opposite positive and negative charges after completion of the non-conduction state, a new object to be adsorbed is adsorbed and held by a large attracting force.